Direct-reading multispeed speedoscope



Oct. 31, 1933. T. A. E. BELT DIRECT READING MULTISPEED SPEEDOSCOPE Filed Dec. 23, 1930 N SUN HUUR h VIUUR Inventor-z Thomas AE. Belt.

by MM His Attorney.

Federated @ct. 311, i933 LUNETED STATES DIREilT-READWG MULTISPEEU SIEEID (OSCGPE Cihomas A. E. Belt, fichenectady. N. Y assignor to General Electric @ompany, a corporation of New York Application December 23, 1930 Serial No. 504,36)?

2 Claims.

My invention relates to phonograph apparatus, particularly to stroboscopic speed indicating devices therefor, and has for its principal object the provision of a direct reading speed indicating 5 device of this character tor determining when phonograph records are rotating at the speed proper thereto.

it has been suggested heretofore to utilize the strohoscopic efiect in determining when a given Ml phonograph record or" a plurality of records adapted each to have a difierent speed of rotation is rotating at its proper speed. A device of this charactenpreviously employed comprises a disk resting on the record and rotated thereby and having marked on its upper surface concen trio rows of stripes or bars, each row consisting of a difierent number of these markings. when this disk is rotating under a suitable periodically varying or intermittent light source, having a 0 period for example of 60 cycles, different rotation speeds of records carrying the disk may he determined, such as 78, 80 or 90 revolutions per min ate, the row of bars or stripes which correspond to a given speed of rotation appearing to he sta- Zt tionary when this given speed is reached.

It is a serious disadvantagepf the above de= scribed system for determining when a given record has reached its proper'speed of rotation that the difierent rows of stripesv or bars which appear stationary on the surface of the disk as the-proper speed is reached for a given record do not give a direct reading of the revolutions per minute proper to this record, or directly indicate and positively identify the given record.

In accordance with my invention this disadvantage is obviated by replacing'the rows of bars or stripes on the surface of the disk above de scribed by rows of indicia, such as numbers, words, or distinctive characters, the respective 40 rows of indicia corresponding respectively to phonograph records adapted to be rotated each at a different speed, the system thus providing a direct-reading instrument.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. l is a perspective View of a phonograph apparatus in which my invention has been embodied; Fig. 2 is an enlarged fragmentary view of the stroboscopic disk shown in Fig. 1 having numbers marked thereon reading the revolutions per minute of a rotating record; and Fig. 3 is a view of a disk similar to that of Fig. 2 but having words marked thereon identiiying records adapted respectively to be rotated at difierent speeds.

In the embodiment of my invention illustrated in Figs. 1 and 2 a phonograph 1c is shown pro- (Cl. Mm -M) of records 12 one of which 13 is shown as mounted in position for rotation. It will be understood that the plurality of records 12 comprises records which are adapted respectively to be rotated at speeds differing each to each; for example, one record or group of records rotating at 78 R. P. ll L, another at to R. P. M. and a third at 90 R. P. M. In order to indicate directly when a given record, as 13, shown in operating position on the turntable 11, is rotating at the speed proper thereto, there is provided in accordance with my invention a member id, preferably a disk, resting upon and rotated by the record 13 and having rows 15 ct indicia thereon which in the disk shown in Fig. 2 are constituted by three concentric rows of equally spaced numbers, the outer row 17 being formed by the radially arranged figures 7 the middle row 13 by the radially arranged figures 3 and the inner row 19 by the radially arranged 9 figures 3 In order to produce the required with sumcient sharpness, it may he found preierable to illuminate the indicia on the rotating disk it by means of a light source in which the light is extinguished each. hall cycle, such. for example, as a neon glow lamp, or a high voltage spark apparatus.

in operation of the, system shown in Fig. l and comprising the disk it shown in Fig. 2, since the rows of numbers on disk 14% are accurately located with reference to each other and since the numbers comprised in each row are accurately spaced, the disk will read directly the revolutions per minute of the rotating record 13 when one or the rows of numbers 15 appears to stand stationary *while rotating in the periodically varying illumination provided by light source 16. The formula for determining the correct number of groupsof indicia such as gar-g comprised in the con- P R.P.M. (1) Where N=nuinber of groups of indicia in a given row. f=irequency in cycles per second of the light source. R. P. M.=revo1utions per minute of the record which carries disk 14. I

Solving Equation (1), the following results are obtained, for i=:

R.P. M. N

the radially arranged numbers 2 in row 17,

when these numbers appear stationary under the illumination of lamp 16 will be 78,2608 R. P. M. the speed indicated by this row 17 being only 3/10% in error. For 80 R. P. M. and for 90 R. P. M. of the disk 14 the numbers of groups of indicia are whole numbers, being respectively 90 forthe center row 18 and 80 for the inner row 19, and, therefore, for these latter two rows the indicated speed of rotation is exactly as given by the numbers constituting these rows when these numbers appear stationary under the illumination of the lamp.

In the embodiment of my invention comprising the form of indicia illustrated in Fig. 3, the

rows of radially arranged members 2 s and? are replaced by words which serve to identify phonograph records which respectively may or may not be of different manufacture but which in any case are characterized by being adapted to be rotated each at a speed different from that of the others. Thus in the embodiment of the invention comprising the disk shown in Fig. 3, in the outer row 20 of this disk the work Victor has been written, it being readily understood that when the correct speed, 78 R. P. IVL, for operating a Victor record is reached the words, Victor, constituting this outer row in place of the numbers 2 shown in row 1'? of Fig. 2, will appear stationary under the ilumination of the periodically varying light source 16. In the second row 21, of Fig. 3 the numbers 3 in row 18 of Fig. 2 are replaced by the word Edison, this word indicating 80 R. P. M., which is the correct speed for operation of Edison records. The inner row 19, of numbers 3 shown in Fig. 2 is replaced by the row 22 constituted by the repetition of the word Foreign", this word indicating 90 R. P. M., which is the speed at which certain records of foreign manufacture are operated.

It will be seen that in the use of the stroboscopic system described in connection with Fig. 3 the operator of the phonograph is given a direct indication of the correct speed of the phonograph turn-table when the words Victor, Edison, or "Foreign, corresponding to the particular type of record being used, appear stationary when illuminated from a 60 cycle light source. The operator need therefore only note the manufacture of the record being used and thereafter adjust the speed of the turn-table until the name or word corresponding to this particular type or manufacture of record appears stationary. It will readily be seen that the names or words identifying different types of records, as above described, may be replaced by tradermarks or other characters distinctive of and serving to identify the records to which they correspond.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a phonograph apparatus Which is adapt-= ed for sound reproduction from a plurality of different records each of which records requires a different speed of rotation for the satisfactory reproduction of sound therefrom, stroboscopic means to determine when a given one of said records is rotating at the speed proper thereto, said means comprising a rotatable element bearing a plurality of rows of words, said element being adapted to rotate in unison with said given record and means to illuminate said words intermittently, the words of each of said rows being identical and different from the words of the others of said rows, the words of a given one of said rows of words corresponding to one only of said records, said words indcating, when a row thereof appears to stand stationary while rotating with the record corresponding thereto, that the record is rotating at the speed proper thereto.

2. In a strobescopic system for determining the speed of rotation of a plurality of phonograph records each requiring a diiferent speed of rotation for the satisfactory reproduction of sound therefrom, each of said records being identified by a different word, a member adapted to be rotated by said records, said member having marked thereon a plurality of concentric rows of words, the words of each of said rows being identical, said difierent words of said member being the same respectively as the different words corresponding to said plurality of records. 

